Although gasoline is the predominant fuel used in many internal combustion engines, it is well known that such engines may be operated by any of a variety of different fuels. For instance, ethanol, methanol, butane, and others may also be used. In fact, with the increasing cost of hydrocarbon fuels (e.g., gasoline) and fluctuations in global supplies, the use of other fuels has received increased interest. However, since most internal combustion engines and their carburetors are designed for efficient use of gasoline, other fuels generally cannot be used effectively without changes to one or both of the engine itself or its carburetor. Such changes are necessary because each fuel operates on a particular air/fuel ratio (i.e., the stoichiometric mixture) for most efficient combustion.
For example, the stoichiometric air/fuel ratio of gasoline is about 14.6 units air to 1 unit of fuel. In contrast, the ratio for ethanol is about 9 to 1, and the ratio for methanol is about 6.5 to 1. Although many available fuel products are made up of mixtures of these materials (e.g., E20, E85), it is still apparent that the preferred operating conditions for using these different fuels in an internal combustion engine can vary greatly.
Accordingly, it would be advantageous for an internal combustion engine to be capable of operating using any of a variety of different fuels without requiring a dedicated carburetor for each fuel. Further, it would be favorable for the configuration of such an engine to be easily switched to provide the preferred operating conditions for the fuel being used.